In this dissertation, I present my contribution towards the understanding and prediction of the risk of CO2 leakage through natural pathways (i.e. faults and fractures). The main portion of this dissertation deals with geomechanical aspects of CO2 Sequestration in Teapot Dome, WY, a mature oil field. The last study investigates the use of induce microseismicity to enhance permeability and injectivity in tight reservoirs and to monitor carbon sequestration projects.
In the first three projects, the Tensleep Formation, a Pennsylvanian age eolian fractured sandstone, is evaluated as the target horizon for a pilot CO2 EOR-carbon storage experiment, in a three-way closure trap against a bounding fault, termed the S1 fault. In the first study, a geomechanical model of the Tensleep Fm. has been developed to evaluate the potential for CO2 injection inducing slip on the S1 fault and thus threatening seal integrity. The geomechanical analysis demonstrated that CO2 sequestration will not induce slip on the reservoir-bounding fault, nor is cracking the cap rock a concern.
In the second study, a 3D reservoir model and fluid flow simulation of the Tensleep Fm., under these geomechanical constraints, was developed to model the migration of the injected CO2 as well as to obtain limits on the rates and volumes of CO2 that can be injected without compromising seal integrity. The results of the numerical simulations corroborate the analytical results of the geomechanical analysis that seal integrity will not be compromised by the pilot injection.
In the third study, we test an Amplitude Versus Angle and Azimuth (AVAZ) analysis to identify the presence of fractures using wide-azimuth 3D seismic data. The objective of the project was to obtain a 3D characterization of the fracture network on both the reservoir and the caprock that will allow for a more accurate assessment of the impact of these features in reservoir permeability and in the risk of CO2 leakage. The AVAZ results were calibrated with fracture intensity and orientations obtained from FMI logs recorded in the area as well as stress orientation and the macro fault network of the anticline.
In the final project of this dissertation, we focus on deep saline formations, which have great potential for geologic sequestration of CO2.
In this study, we investigate the use of induced microseismicity to enhance permeability and injectivity of a tight formation as well as to monitor a carbon sequestration project. During the injection-induced microseismicity stimulation, more than 10,000 metric tons of supercritical CO2 were injected into the Bass Island Dolomite (BILD) during a period of 40 days. A total of 803 events were recorded in more of three sensors in each of the two monitoring arrays. However, no definite seismic activity could be related to the injection in the BILD. A preliminary possible hypothesis relates this microseismicity to a CO2 injection from a deeper and preexisting FOR project in this area, which could be migrating upwards along the monitoring wells. (Abstract shortened by UMI.)